This invention relates generally to detectors used in imaging systems, and more particularly, to solid state detectors configured to acquire multi-modality image data.
The cost of imaging systems is often prohibitive. Therefore, multi-modality imaging systems which are capable of scanning using different modalities, such as Positron Emission Tomography (PET), Single Positron emission tomography (SPECT), Nuclear Medicine (NM), Computed Tomography (CT), static X-ray imaging, and dynamic (Fluoroscopy) X-ray imaging are desirable. Also, a patient may be better diagnosed by comparing images acquired using different modalities. Unfortunately, it is often difficult to achieve the same view of a patient's anatomy using two different acquisition systems. Also, currently available multi-modality imaging systems often use multiple detectors with each detector being dedicated to a specific modality, limiting the flexibility of the system.
With current systems, when acquiring CT scans, the flux, or count rate, of X-ray photons often exceeds the system's capacity for counting the photons. For example, the photon flux for diagnostic CT may reach 100 MHz. Therefore, currently available solid state detectors which acquire CT data are used in current mode. Each pixel has a corresponding data channel. The signal is input to a current integrator, and then converted with an analog to digital converter (ADC). An average number of photons for a period of time are provided rather than a precise count. Current mode detection also adds noise to the signal and may require a high X-ray dose which both adversely effects living tissue and necessitates a large, expensive X-ray tube that consumes a large amount of energy and produces a large amount of heat requiring additional cooling systems. In addition, the ADC needed to provide a high level of accuracy is expensive.
When acquiring SPECT or NM data, each pixel has a corresponding data channel. The input signal is analyzed and compared to an energy range. If the input signal is less than a minimum energy value or greater than a maximum value, the signal may be rejected. Valid signals are digitized, using ADC for several or all of the pixels.
Therefore, a need exists for a system capable of acquiring patient data representative of more than one type of radiation data, which increases the flexibility and accuracy with which patient data is acquired and to address the problems noted above. Certain embodiments of the present invention are intended to meet these needs and other objectives that will become apparent from the description and drawings set forth below.